[POC] Add UT for installer command.

tests/kvmtest.sh

@@ -201,6 +201,7 @@ test_t0_sonic() {
     # TODO: Use a marker to select these tests rather than providing a hard-coded list here.
     tgname=t0-sonic
     tests="\
+      platform_tests/cli/test_not_depends_on_database.py \
       bgp/test_bgp_fact.py \
       macsec/test_macsec.py"
 

tests/platform_tests/cli/test_not_depends_on_database.py

@@ -0,0 +1,52 @@
+"""
+Tests for the `sonic_installer` commands in SONiC
+"""
+import logging
+import paramiko
+import pytest
+import time
+
+from tests.common.helpers.assertions import pytest_assert
+from tests.common.utilities import skip_release, wait_until
+from tests.common.platform.processes_utils import wait_critical_processes
+from tests.common.config_reload import config_reload
+
+pytestmark = [
+    pytest.mark.disable_loganalyzer,
+    pytest.mark.topology('any'),
+    pytest.mark.device_type('vs')
+]
+
+DOCKER_WAIT_TIME = 10
+
+@pytest.fixture(scope='function')
+def stop_database_docker(duthosts, enum_rand_one_per_hwsku_hostname):
+    duthost = duthosts[enum_rand_one_per_hwsku_hostname]
+
+    # save config for reload later
+    duthost.shell('sudo config save -y')
+
+    # shutdown database docker before test
+    duthost.command("sudo docker stop database", module_ignore_errors=True)
+    time.sleep(DOCKER_WAIT_TIME)
+
+    yield
+
+    # start database docker after test
+    duthost.command("sudo docker start database", module_ignore_errors=True)
+    time.sleep(DOCKER_WAIT_TIME)
+
+    # reload config, because some critical process not work after database docker restart
+    config_reload(duthost, config_source='config_db', safe_reload=True)
+
+def test_installer_not_depends_on_database_docker(duthosts, enum_rand_one_per_hwsku_hostname, stop_database_docker):
+    """
+    @summary: Test sonic-installer command can work when database docker not running
+    """
+    duthost = duthosts[enum_rand_one_per_hwsku_hostname]
+    skip_release(duthost, ["201811", "201911", "202012", "202106", "202111"])
+
+    # test installer command
+    sonic_installer_result = duthost.command("sudo sonic-installer list")
+    pytest_assert(sonic_installer_result["stdout_lines"][0].startswith("Current:"),
+                  "sonic-installer command failed, stdout: {}, stderr: {}".format(sonic_installer_result["stdout_lines"], sonic_installer_result["stderr_lines"]))